title: Electrostatic origin of in vitro aggregation of human γ-crystallin.
abstract: The proteins α-, β-, and γ-crystallins are the major components of the lens in the human eye. Using dynamic light scattering method, we have performed in vitro investigations of protein-protein interactions in dilute solutions of human γ-crystallin and α-crystallin. We find that γ-crystallin spontaneously aggregates into finite-sized clusters in phosphate buffer solutions. There are two distinct populations of unaggregated and aggregated γ-crystallins in these solutions. On the other hand, α-crystallin molecules are not aggregated into large clusters in solutions of α-crystallin alone. When α-crystallin and γ-crystallin are mixed in phosphate buffer solutions, we demonstrate that the clusters of γ-crystallin are prevented. By further investigating the roles of temperature, protein concentration, pH, salt concentration, and a reducing agent, we show that the aggregation of γ-crystallin under our in vitro conditions arises from non-covalent electrostatic interactions. In addition, we show that aggregation of γ-crystallin occurs under the dilute in vitro conditions even in the absence of oxidizing agents that can induce disulfide cross-links, long considered to be responsible for human cataracts. Aggregation of γ-crystallin when maintained under reducing conditions suggests that oxidation does not contribute to the aggregation in dilute solutions.
authors.affiliation: Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Mohr
authors.forename: Cassidy M
authors.initials: CM
authors.lastname: Dobson
authors.forename: Scott C
authors.initials: SC
authors.lastname: Garman
authors.forename: Murugappan
authors.initials: M
authors.lastname: Muthukumar
mesh_terms: D003001:Cloning, Molecular; D006801:Humans; D008027:Light; D011485:Protein Binding; D017510:Protein Folding; D012542:Scattering, Radiation; D012996:Solutions; D055672:Static Electricity; D038222:gamma-Crystallins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D012996:Solutions; D038222:gamma-Crystallins